1. Field of the Invention
The present invention relates generally to subsea pipeline hot tapping operations, and more particularly relates to subsea pipeline fluid blasting operations conducted through a pipeline hot tap.
2. Description of the Related Art
Subsea crude oil pipelines are often plugged by localized accumulations of paraffin, hydrate and other deposits. A paraffin blockage is caused by the paraffin precipitating out of the crude oil and packing in the pipe. The paraffin is very waxy and can clog or plug the pipeline. Plugging of pipelines is a well known problem. Pipeline operators attempt to prevent this problem by requiring regular pigging of the pipeline or through the injection of solvents or chemicals in the pipeline to prevent paraffin build-up.
Nonetheless, plugging of pipelines does occur. Typically, the paraffin blockage is removed from a subsea pipeline by raising the pipeline to the surface and severing the pipeline. The pipeline can then be mechanically cleaned or the plugged section replaced. With the plug removed, the pipeline is reconnected and lowered back down to the sea floor.
It is desirable to have an apparatus and method of using the apparatus for removing any blockage in a subsea pipeline due to paraffin or hydrates or other materials that may percipitate from crude oil, and more generally to blockages of any sort that can be removed by fluid blasting or chemical decomposition. It is also desirable to be able to remove a plug in a subsea pipeline without retrieval of the pipeline to the surface. It is also desirable to be able to remove a plug in a subsea pipeline without severing the pipeline. It is also desirable to be able to remove the plug with the pipeline under pressure while protecting the environment from oil spills.